It has become a common practice to package convenience foods in disposable cooking or heating utensils made of coated paperboard. Due to the increased popularity of microwave cooking, substantial efforts have been made to provide dual-ovenable containers which are suitable for both conventional oven and microwave oven cooking. Accordingly, a number of polymeric plastic paperboard coatings have been developed to protect paperboard containers and their contents from the temperature extremes associated with cold storage and heating. For example, U.S. Pat. No. 3,813,256 discloses food heating utensils made of paperboard coated with polyphenylene oxide or polysulfones. The use of paperboard products coated with polypropylene or polyester are disclosed in U.S. Pat. Nos. 3,904,104 and 4,147,836. U.S. Pat. No. 4,421,825 discloses the use of titanium dioxide in coatings to give the paperboard resistance to browning.
There is a growing market demand for disposable paperboard for use in baking applications with food products such as cinnamon rolls, biscuits, and the like. However, these foods have proven to be difficult to successfully package in that they have a tendency to stick to the paperboard when baked. As sugar tends to caramelize upon heating, this adherence problem is particularly pronounced in those cases where the packaged food contains high levels of sugar.
Dual-ovenable food trays are disclosed in U.S. Pat. No. 5,494,716; while U.S. Pat. No. 5,002,833 discloses polymethylpentene (PMP) extrusion-coated paperboard of the type currently utilized for ovenable baking applications. Although PMP paperboard can exhibit good grease resistance, heat resistance, and food release characteristics, the high material and processing costs associated with PMP paperboard makes this type of coated paperboard relatively expensive to use. Moreover, PMP paperboard may prove to be somewhat difficult to recycle.
Therefore, an object of this invention is to provide aqueous compositions for coating ovenable paperboard suitable for use in producing food trays for baking applications.
A further object of this invention is to solve the baking product adherence problem by providing ovenable coated paperboard which exhibits good grease resistance, high heat resistance and good food release characteristics.
Yet another object of this invention is to provide a dual-ovenable food tray coated with an aqueous coating composition that performs without grease seepage, browning, and emission of odors during cooking.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows.